Two position pitch-changing mechanism



Dec. 28, 1948.

2 Sheets-Sheet l Filed oct. 15, 1945 -Y INVENTOR.

/fo'fwe A Poy Patented Dec. 28, 1948 TWO POSITION 'FITCH-CHANGING MECHANISM vIIorace H. Roby, Wichita, Kans.

Application October 13, 1945, Serial No. 622,180

This invention relates to improvements in a 3Y claims. (c1. 17o-162) two position pitch-changing meehanismand` refers more particularly to an automatic pitchchanging device for controllable pitchpropellers for airplanes. In the operation of an airplane it is important at all items to have the, advantage of maximum power of the engine.

This-is par- I ticularly essential when the plane .is taking off.

just the blades in a lo-w pitch position and with the decrease of the rotative speed to automatically move the blades to a high pitch position.

.Another object of the invention is to provide a pitch-changing device particularly adapted to small planes and low horsepower motors `which delivers the maximum horsepower of the engine when the plane takes off or whileit is being air borne by adjustment of the propeller-blades in a low pitch position. y

A further object is to providea pitch-changing mechanism adapted to automatically adjust the propeller blade pitch to a high pitch position when the engine speed is decreased after take-oli to a cruising speed.

Other and further objects will appear from the v following description. y a

In the accompanying drawings which form a part of the instant speciiication and are to be read in conjunction therewith, and in which like reference numerals indicate like parts in the various views,

Fig. 1 is a rear view of a two blade propeller hub assembly embodying the invention with the blades broken away,

Fig. 2 is a central section of the device shown in Fig. l,

Fig. 3 is a top plan of the propeller shown in Fig. l with the blades adjusted in a low pitch position and with parts of the pitch-changing mechanism broken away, and

Fig. 4 is a similar View to Fig. 3 with the blades adjusted in a high pitch position.

Referring to the drawings, at Ill are shown the `propeller blades broken away in Figs. l and 2.

The hub ends of the blades are pressed into sleeves IIand rigidly aiixed thereto by lag screws, the heads of which are shown at l2.

A driving spider I3 is fixedly mounted upon the propeller shaft of the airplane, not shown. Extending radially from spider I3 are shanks I3a upon which are mounted roller bearings I4 which carry the blade retention sleeves II. `Bearings I4 set into a machined portion of the sleeves and are held in place by the lock rings I5 fitting in grooves in the Shanks and retaining nuts I6 screwed into internal threads at the end of retention sleeves Il. Seal rings IEa inside the retaining nuts abut against the Shanks and seal The skirts ofthe caps overlap thelock rings and prevent displacement.` I

Within a cavity` in each of the Shanks is a lead weight I9 held in place by a threaded stud upon which is screwed a holding nut'ZI. On the hub ends of the sleeves IlV are affixed clamping rings 22 held in place by bolts 23 which are screwed into threaded ears 22a shown in Figs. 3 and' 4,

Attached to separate ears 22h of the clamping rings are lugs 24 whose outturned pin extensions 24a slide in Isemicircular cam slots in the circular ring or pitch-changing member 25. The pitchchanging member or cam ring 25 is rotatably mounted on the sleeve portion of spider I3, as shown in Fig. 2. Outside of the cam ring and also freely rotatable upon the sleeve of the spider are ily weights 26.` In a well formed in the cam ring is a pin 2l resiliently cushioned by coil spring 28 serving as a stop for a pin 29 extending from the rear of one of the fly weights and permitting Y passage of the pin when the fly weights have considerable rotative inertia.

The operation of the mechanism is more or less obvious from the description. When the engine is started and the propeller is rotated in a clockwise direction as shown by the arrow in Fig.

1, the starting inertia of the fly weights freely and gradually increase the rotative speed of the fly weights until the pins rest in abutment and the fly weights rotate with the cam ring. The low pitch adjustment of the propeller blades will continue so long as the propeller is rotated at high speed and maximum power is desired.

After the take-off and the plane is in the air and when the engine speed is reduced to its cruising rate, the propeller speed isreduced with the engine speed but the rotative speed of the fly weights does not immediately respond to the reduction in speed of the propeller. This causes thei fly weights to overrun the speed of,thecam.ring y. and propeller, moving rotating pin 29 around!-y the periphery of the cam ring to abutment'onw` Thislrotatesthe the opposite side of stop 2l.

cam ring through an arc correspondingv to the-I length of the cam slots while the pins 24a slidposition--shown in Fig. 3 to the high pitch posiv tionshown in Fig. 4. .Slight depressions 25a on theinner surface of the cam slots at the high pitchend hold the propeller in high pitch position through the centrifugaltwisting moment and air loadsof the blade,y allowing for minor throttle settings andsmall inertia changes in the fly weights.l

.If the'inertia of the fly weightsis too great, whether speed is being increased or decreased, stop pin 2l is depressed allowing the fly weights tc over-run the cam and propeller speed or rotate'at a slower speed than .the cam and propeller sleeve until speed of the fly weights is either reduced or increased to more nearly correspond to the speed of the propeller at which time the stop and ily weight pin engage when the fly weights and propeller rotate together.

The lead Weights i9 in the cavities of the Shanks may b e varied to statically balance the propellerk I,'Ihusit willbe seen that the pitch-changing mechanism operatesautomatically to shift the blades into low pitch position when maximum power of the ,enginel is needed and the rotative speed of the propeller is rapidly increased. With reduction of engine speed the mechanism automatically operates to shift the propeller bladesy from low to high pitch thus providing high propellerfefficiency under all operating conditions of the plane. When making a landing, if` the field has been misjudged or an obstacle appears and there is need for an emergency'take-off or'the use of the engines maximum power, sudden increase of engine speed by opening the throttle will automatically shift the propeller to low pitch position.

From the foregoing it will be seen that the'in-` vention is well adapted to attain the objects hereinbefore set forth together with other advantages which are obvious and which are inherent to the structure.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.

As many possible embodiments may be made of.. the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the drawings is to be interpreted as illustrative and not in a limiting-sense.-

Having thus described my invention, I claim: nu1..A. two position pitch-changing mechanism for a controllable pitch propeller whose hub assembly includes a blade-supporting spider mounted on the propeller shaft, radial Shanks on the spider-and mountings on the hub ends of the blades axially rotatable on said Shanks, a ily weight assembly freely rotatable with respect to thepropeller shaft, a pitch changer plate also rotatable with respect to the propeller shaft and lsaid-plate:having arcuate cam slots permitting :25J movement of said changer through an are corresponding to the range of the pitch change of theiblades, separate blade actuating means slidable-1 inthe slots of the pitch changer and each `)connected to a blade mounting, contacting mem- Lbers on the fly weight assembly and pitch changer platev operable with increase and decrease in the rotative speed 0f the propeller to shift the pitch changer. l

2. A pitch-changing mechanism as in claim l """inwhich the contacting members on the fly weight assembly and pitch changer plate comprise stationary and retractible contacting abutments on ther fly weights and pitch changer.

3. A pitch-changing mechanism as in claim 1 40 "having depressions formed in the ends of the cam slots whereby shifting of the slidable means due to minor speed changes and small inertia changes of the ily" weight assembly is retarded.

` HORACE H. ROBY. Y

REFERENCES CITED The Afollowing `references are of record in the le of Athis patent: 

